Eileen the Crow
So, I have no idea how to do this. But I think if you kill Rom without doing Eileen's quest line, she gives in to her thirst for blood and you fight her at the Grand Cathedral instead of fighting the Bloody Crow of Cainhurst. As you might expect, she's a whole lot weaker than the crow, and she's relatively easy to kill. I killed her by using her own methods against her; quickstepping. Like I said, I have no idea how to do this but still, it was my first time experiencing it so I wanted to share it.